Can you use this in a frit casting mould, like the Beach Shells mould for example?

No, we do not recommend Economy Boron Nitride Spray for casting moulds. You may experience poor separation of the glass. For casting moulds, and ceramic moulds in general, if you want to use Boron Nitride, we would recommend the ZYP Spray.

This Economy Boron Nitride spray is good for using with stainless steel moulds, where we have found it to be effective in our tests.